I use UniversalMouse for scrolling, and I happen to have my
middle mouse button mapped both to double-click and universal
scroll. The scrolling doesn't work under R5's ShowImage for
some reason, but to my delight, under Haiku's it does!
However, it also selects a filled-in area the colour of
whatever pixel was under the mouse when you start scrolling.
On click, you can see it start to select, then scrolling is
fine (it doesn't follow around/actually select anything yet),
then when you let go of the middle button, it starts following
the mouse, filling in solid. As the mouse moves, it flickers
between solid and transparent, but when you're not moving,
it's solid black or white or whatever was under the mouse when
you started. Clicking and right-clicking won't disable it--at
this point I have to press escape to get it to go away.
Other than that, really solid app. Works very well, and I love
the alt-up alt-down feature. If only I can figure out what
these Browse features do...